Andarair Gomes dos Santos

Rheological and some physicochemical characteristics of selected floral honeys from plants of caatinga

The aim of this paper was to investigate the physicochemical characteristics and rheological behavior of some floral honeys from species of wild plants found in the Caatinga biome, as well as, correlate honey viscosities with its chemical composition. Thus, five honeys with floral predominance of typical plants foraged by honeybees in Caatinga were analyzed. Results showed that moisture content of honeys ranged from 17.45 to 21.50 g/100g. The samples exhibited higher fructose content (37.58 - 43.95 g/100g) and lower glucose content (27.41- 33.80 g/100g). The glucose-water ratio ranged from 1.55 to 1.80. Sucrose contents, excluding Croton campestris honey sample, exhibited values above the highest sucrose content (6.0 g/100g) allowed by Brazilian norm. The ash content ranged from 0.02 to 0.19 %. The insoluble solids content were above 0.1 g/100 g. The electrical conductivity ranged between 144.90 and 412.55 µS.cm-1. All the honey samples behaved as Newtonian fluids. The viscosity values, measured at 293 K, varied from 1.90 to 8.55 Pa.s. An empirical mathematical model adapted from the Arrhenius model provides a good description of honey viscosity as a function of combined effects of temperature and moisture content.

Síntesis y Refinado por el Método Rietveld de la fase perovsquita obtenida a partir del Método de Co-precipitación vía Oxalato

Powders of perovskite SrCo0.8Fe0.2O3-δ were synthesized using oxalate co-precipitation method. According to the thermal gravimetry and differential thermal analysis (TG/DTA), total mass loss was 40 % corresponding to three different steps and the precipitant agent as well the starting chemical elements have no influence on the process. Perovskite phase was identified by x-ray diffraction and the average crystallite size was 77.22 nm using iron nitrate (III) as starting material while 42.23 nm were obtained using iron oxalate (III). Ammonium oxalate and equimolar mixtures of ammonium oxalate and oxalic acid were used as precipitant agents and the results shown that these reactants have no influence on the average crystallite size (42.95 nm and 42.23 nm). The material presents isotherms of type II, with especific surface of approximately 4,41m 2 g -1 .

Desenvolvimento de um kit de reator de leito fixo de bagaço de cana-de-açúcar para uso didático

E de fundamental importância o desenvolvimento de praticas de laboratorio nos cursos de engenharia, porem os altos custos dos kits didaticos muitas vezes inviabilizam sua aquisicao. No entanto, o presente trabalho teve como objetivo desenvolver um kit para aulas de cinetica e reatores, utilizando materiais de facil aquisicao e com carater ambiental, uma vez que o leito fixo e composto por bagaco de cana-de-acucar. Para estudar a cinetica, variou-se o volume de alcool etilico alimentado e a altura de leito fixo no reator, observando o comportamento do rendimento e da produtividade. Avaliou-se a influencia da adicao do alcool etilico e acido acetico na producao deste e avaliou-se a atividade operacional do recheio atraves do reuso do mesmo. A acidez do produto aumentou com o passar do tempo e apos cerca de 12 horas manteve-se constante. O rendimento teve um aumento proporcional a diminuicao do volume de alimentacao e ao aumento da altura do leito fixo. Aplicando os valores obtidos em modelos de cinetica de primeira e segunda ordem, concluiu-se que o modelo cinetico de primeira ordem se ajustou melhor aos dados obtidos.

AVALIAÇÃO DE PROPRIEDADES FÍSICAS E QUÍMICAS DE ELETRODEPÓSITOS DE Ni-W-P OBTIDOS EM CÉLULA DE HULL

Ni–W–P electrodeposits were synthesized in a Hull cell in order to simulate the obtainment under industrial conditions. Complete coverage of panels was accomplished by applying total currents of 1.0 and 2.0 A. Panels obtained with a current of 1.0 A appeared brighter. The best compositional uniformities, as determined by Energy Dispersive Spectrometer (EDS) occurred in the current density ranges of 0.6 to 3.0 A dm−2 and 1.6 to 6.0 A dm−2 obtained with 1.0 and 2.0 A, respectively. However, the best morphological characteristics, as determined by Scanning Electro Microscope (SEM), were observed in those obtained with a total current of 1.0 A. Analysis of corrosion resistance by Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Linear Polarization (PLP) in NaCl have shown significant variations in the amount of corrosion potential, polarization resistance, and even total impedance. The alloys exhibited amorphous character (XRD) and crystallized above 400 °C to Ni and Ni3P phases, and possibly Ni–W, with a subsequent increase in hardness. The results suggest that under industrial conditions, current density variations due to the large and complex geometric shapes of substrates lead to formation of distinct alloys. Furthermore, these materials are potential substitutes for chromium deposits in many applications.